In a small bowl, combine the sour cream, cumin, and ¼ teaspoon of the salt. Cover and refrigerate.
Heat the oil in a large saucepan over medium-high heat. Add the garlic and cook for 1 minute.
Add the tomatoes and their juices, the pepper, and the remaining salt and bring to a simmer. Cook for 10 minutes.
Add the jalapeños or hot sauce and hominy and simmer for 5 minutes.
Add the shrimp and simmer until pink and cooked through, 3 to 4 minutes.
Ladle the soup into bowls, top with a spoonful of the cumin cream, and sprinkle with the cilantro (if desired). Serve the lime on the side.